Hi, We are a similar family to yours. My daughter is 7 now and we leave tomorrow for Madrid. When we took her at 5 months old, I found everything I needed there. I used formula here (Carnation Good Start) and they have it there under the Nestle name. You will buy the formula and baby needs at a farmacia and they should have your type of formula there as babies over there are no different, no?
I would suggest that you have a family member there go and double check with a pharmacy before you go just to make sure.
Hope that helps.
BTW, take extra cash for all the beautiful girl clothes and shoes for your little one-The Spaniards dress their babies like royalty!!!! The sales start July 1st!!